The electronic structure of the rare-earth intermetallic compound La0.73Tb0.27Mn2Si2 has been studied by resonant photoemission spectroscopy using synchrotron radiation, and its formation patterns have been established upon partial replacement of lanthanum atoms by terbium. The dependence of the valence band spectra shape on the photon energy near the absorption edges of the internal levels of manganese, lanthanum, and terbium is analysed. The processes of direct and two-stage production of photoelectrons, elastic and inelastic decay channels of these states with the emission of high-energy electrons due to intra-atomic Coulomb interaction have been studied. The dominant mechanisms of the decay of the excited states of the components under study were determined from the shapes of the spectra. For rare-earth metals elastic decay channel of the excited state is the most probable, while for manganese, it is inelastic, with the formation of a second hole in the valence band with subsequent enhancement of photoemission. Exciting photoemission near M5-absorption edges of rare-earth elements, the main contribution to the valence band comes from terbium 4f-states. Exciting photoemission near L3-absorption edge of manganese, the main contribution to the valence band is made by manganese 3d-states; with an increase in the photon energy in the region after resonance, an Auger channel for the decay of the excited state arises in the form of intensity maximum shift towards the binding energy growth. Features of the topography and magnetic domain structure of the La0.73Tb0.27Mn2Si2 surface were studied by atomic force and magnetic force microscopy at room temperature.